In order to improve the effective light-emission efficiency for semiconductor light-emitting devices, materials such as Ag and Al having superior light reflectivity are used to form an electrode layer for the mounting of an element and/or a reflective layer for reflecting light from the element on an element mounting surface or a reflection surface of a substrate of a semiconductor light-emitting element mounting member (e.g., see Japanese Laid-Open Patent Publication Number 9-293904 Claims 1, 2, sections 0015-0017, FIG. 1, FIG. 2, Japanese Laid-Open Patent Publication Number 2002-217456 sections 0013-0014, FIG. 1, FIG. 2, and Japanese Laid-Open Patent Publication Number 2002-232017 Claim 1, sections 0016-0021, FIG. 1).
While Ag, Al, and the like provide superior light reflectivity, the metal films actually formed on the element mounting surface, the reflective surface, or the like on the substrate do not provide adequate surface smoothness. This results in the irregular reflection of light and prevents a high effective reflectivity from being obtained.
In high-output semiconductor light-emitting devices with outputs of at least 1 W, which have undergone rapid development in recent years, high current flows make it necessary for the metal film used as the electrode layer to be thick so that the resistance can be lowered. However, with thicker metal films there is a greater tendency for the surface to be irregular. This prevents a high reflectivity from being obtained.
Also, this reduction in reflectivity is especially prominent with light having short wavelengths of no more than 450 nm in semiconductor light-emitting devices for ultraviolet emission and semiconductor light-emitting devices that emit white light in combination with a fluorescent material. The more uneven the metal film surface is, the more significant the reduction in effective reflectivity for light with short wavelengths is.
Furthermore, in recent years, the use of flip-chip mounting using Au bumps has become widespread as a method for mounting a semiconductor light-emitting element to a semiconductor light-emitting element mounting member. Flip-chip mounting involves a small contact area between the electrode layer of the semiconductor light-emitting element mounting member and the Au bumps. Thus, providing a practical degree of mounting strength, the adhesion of the metal layer serving as the electrode layer to the substrate must be improved and the mechanical strength of the metal layer itself must be increased.
Also, since Ag, Al, and the like are materials that tend to generate migration, a high degree of reliability cannot be provided in high-output semiconductor light-emitting devices that require high currents as described above.
Thus, a semiconductor light-emitting element mounting member with an improved effective light reflectivity in a metal film serving as an electrode layer and/or a reflective layer is desired.
Further, a semiconductor light-emitting element mounting member in which the metal layer has improved adhesion to a substrate, mechanical strength, and reliability is needed.
Additionally, a semiconductor light-emitting device with superior light-emitting characteristics using the semiconductor light-emitting element mounting member described above is desired.